1. Field of the Invention
The present invention relates generally to integrated circuit chip package technology and, more particularly, to a semiconductor package having a second semiconductor package integrated therein.
2. Description of the Related Art
Semiconductor dies are conventionally enclosed in plastic packages that provide protection from hostile environments and enable electrical interconnection between the semiconductor die and an underlying substrate such as a printed circuit board (PCB) or motherboard. In the field of electronics, there is a continuing evolution of products which are smaller and more complex. As a result, the semiconductor packages incorporated into these products must be smaller and more complex as well.
The elements of currently known semiconductor packages include a metal leadframe, an integrated circuit or semiconductor die, bonding material to attach the semiconductor die to the leadframe, bond wires which electrically connect terminals on the semiconductor die to individual leads of the leadframe, and a hard plastic encapsulant material which covers the other components and forms the exterior of the semiconductor package commonly referred to as the package body. The leadframe is the central supporting structure of such a package, and is typically fabricated by chemically etching or mechanically stamping a metal strip. A portion of the leadframe is internal to the package, i.e., completely surrounded by the plastic encapsulant or package body. Portions of the leads of the leadframe extend externally from the package body or are partially enclosed therein for use in electrically connecting the package to another component. In certain semiconductor packages, the leadframe is substituted with a substrate such as a laminate substrate to which the semiconductor die(s) are mounted. Formed on that surface of the substrate to which the semiconductor die(s) are mounted is a conductive pattern to which the semiconductor die(s) is/are electrically connected through the use of, for example, conductive wires. Formed on the opposite surface of the substrate are conductive pads or contacts which are electrically connected to the conductive pattern in a prescribed arrangement through the use of conductive vias extending through the substrate. The package body is often formed to cover those surfaces of the substrate other than that surface including the contacts formed thereon.
With regard to those semiconductor packages including substrates as opposed to leadframes, one technique used in the prior art for minimizing the thickness of such semiconductor packages is the placement of one or more electronic components (e.g., semiconductor dies, passive devices, etc.) of such package into corresponding cavities or through-hole openings formed in the substrate. However, when a cavity or through-hole opening is made in the substrate, the available surface area of the substrate is effectively reduced, therefore reducing the usable area on which printed wiring interconnection patterns such as the above-described conductive pattern may be formed. In this regard, the increasing need for complex functionality in semiconductor packages as discussed above generates a corresponding need for increased surface area on the semiconductor package substrate upon which interconnection patterns may be formed to accommodate the electronic components of the package.
Another deficiency with currently known semiconductor packages which include either a leadframe or a substrate arises when one or more of the electronic components interfaced to the leadframe or substrate is stress-sensitive (e.g., a crystal). In this regard, during the process of pressure injection molding the package body of the semiconductor package, a crystal which is mounted to the leadframe or substrate may become stressed. Though attempts have been made to place any stress-sensitive component near a surface of the leadframe or substrate that is not in contact with the package body, such placement typically results in the stress-sensitive component being disclosed in close proximity to a surface of the leadframe or substrate used to effectuate the electrical connection between the leadframe or substrate and the electronic component(s) of the package. The resultant electrical interconnection activity near the stress-sensitive component often produces undesirable effects therein. Yet another deficiency arises when certain types of semiconductor dies or other electronic components are directly attached to the leadframe or substrate of the semiconductor package. More particularly, when such devices are subjected to encapsulation stresses during the pressure injection formation of the package body of the semiconductor package, such stresses may result in an operational failure of the devices. As will be recognized, such an operational failure typically mandates that the entire semiconductor package be discarded. Thus, there exists a need in the art for a semiconductor package which avoids the aforementioned deficiencies and shortcomings of currently known semiconductor packages, yet satisfies the demands for semiconductor packages which are of reduced thickness and increased complexity/functionality. These, as well as other features and attributes of the present invention will be discussed in more detail below.